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THE BEST SCIENTIFIC PUBLICATIONS - TETHYS, ENCELADUS, END.......




     
    
         Image Credit: NASA/JPL-Caltech/Space Science Institute










We’ve been getting some fantastic images from 
the Cassini Spacecraft this year as it orbits 
Saturn, and one of itslatest image from the 
ringed planet is no less stunning.Tethys, 
Enceladus and Mimas can be seen alongside 
Saturn’s rings. The picture wa
taken in early December, 2015.
Tethys (660 miles or 1,062 kilometers across) 
appears above the rings, while Enceladus 
(313 miles or 504 kilometers across) sits 
just below center. Mimas (246 miles or 
396 kilometers across) hangs below and 
to the left of Enceladus.This view looks 
toward the sunlit side of the rings from about 
0.4 degrees above the ring plane. The image 
was taken in visible light with the Cassini 
spacecraft narrow-angle camera on 
Dec. 3, 2015.The view was acquired at a 
distance of approximately 837,000 miles 
(1.35 million kilometers) from Enceladus, 
with an image scale of 5 miles (8 kilometers) 
per pixel. Tethys was approximately 
1.2 million miles (1.9 million kilometers) 
away with an image scale 
of 7 miles (11 kilometers) per pixel. 
Mimas was approximately 1.1 million miles 
(1.7 million kilometers) away with an image 
scale of 6 miles (10 kilometers) per pixel.

NASA - Hubble Sees the Force Awakening 

in a Newborn Starhttp



Just in time for the release of the movie 


“Star Wars Episode VII: 


The Force Awakens,


” NASA’s Hubble Space Telescope has 


photographed what looks like a cosmic, 

double-bladed lightsaber.In the center 

of the image, partially obscured by 


a dark, Jedi-like cloak of dust, 


a newborn starshoots twin jets out 

into space as a sort of birth 

announcement to the universe.




This sequence combines a two-dimensional zoom and a three-dimensional flight to explore 
the Hubble Space Telescope's striking image of the Herbig-Haro object known as HH 24.
Credits: NASA, ESA, and F. Summers, G. Bacon, Z. Levay, and L. Frattare (Viz 3D Team, STScI)


“Science fiction has been an inspiration to 



generations of scientists and engineers, 


and the film series Star Wars is no exception,

” said John Grunsfeld, astronaut and associate 

administrator for the NASA Science Mission 

directorate.  “There is no stronger case for 

the motivational power of real science than 

the discoveries that come from 


the Hubble Space Telescope as it unravels 


the mysteries of the universe."This celestial 

lightsaber does not lie in a galaxy far, far away, 

but rather inside our home galaxy, the Milky Way. 

It’s inside a turbulent birthing ground for new 

stars known as the Orion B molecular 

cloud complex, located 1,350 light-years away.

This celestial lightsaber does not lie in a galaxy far, far away, but rather inside our home galaxy, 
the Milky Way. It's inside a turbulent birthing ground for new stars known as 
the Orion B molecular cloud complex, located 1,350 light-years away.
Credits: NASA/ESA



heated 
material spills away and is shot outward from 
the star in opposite directions along an uncluttered 
escape route — the star’s rotation axis.
Shock fronts develop along the jets and heat 
the surrounding gas to thousands of degrees 
Fahrenheit. The jets collide with the surrounding 
gas and dust and clear vast spaces, like a stream 
of water plowing into a hill of sand. The shock fronts 
form tangled, knotted clumps of nebulosity and 
are collectively known as Herbig-Haro (HH) objects. 
The prominent HH object shown in this image is HH 24.

Just to the right of the cloaked star, a couple of 
bright points are young stars peeking through and 
showing off their own faint lightsabers — including 
one that has bored a tunnel through the cloud towards 
the upper-right side of the picture.

This is an artist's concept of the fireworks that accompany the birth of a star. The young stellar 
object is encircled by a pancake-shaped disk of dust and gas left over from the collapse of 
the nebula that formed the star. Gas falls onto the newly forming star and is heated to 
the point that some of it escapes along the star's spin axis. Intertwined by magnetic 
fields, the bipolar jets blast into space at over 100,000 miles per hour. As seen 
from far away, they resemble a double-bladed lightsaber 
from the Star Wars film series.
Credits: NASA, ESA, and A. Feild (STScI)
When stars form within giant clouds of cool molecular 
hydrogen, some of the surrounding material collapses 
under gravity to form a rotating, flattened disk 
encircling the newborn star.
Though planets will later congeal in the disk, at this 
early stage the protostar is feeding on the disk with 
a Jabba-like appetite. Gas from the disk rains down 

onto the protostar and engorges it. Super
Overall, just a handful of HH jets have been spotted 
in this region in visible light, and about the same 
number in the infrared. Hubble’s observations for 
this image were performed in infrared light, which 
enabled the telescope to peer through the gas and 
dust cocooning the newly forming stars and capture 
a clear view of the HH objects.
These young stellar jets are ideal targets for NASA’s 
upcoming James Webb Space Telescope, which will 
have even greater infrared wavelength vision to see 
deeper into the dust surrounding newly forming stars.
The Hubble Space Telescope is a project of international 
cooperation between NASA and 
the European Space Agency. 
NASA’s Goddard Space Flight Center in Greenbelt, 
Maryland, manages the telescope. The Space Telescope 
Science Institute (STScI) in Baltimore, Maryland, 
conducts Hubble science operations. STScI is operated 
for NASA by the Association of Universities for Research 
in Astronomy, in Washington, D.C.


For images and more information, visit:



NASA - Spirals in Dust Around 

A team of astronomers is proposing that huge spiral 

patterns seen around some newborn stars, merely 


a few million years old 


(about one percent our sun’s age), 


may be evidence for the presence of giant unseen 


planets. This idea not only opens the door to 


a new method of planet detection, but also could 


offer a look into the early formative years 


of planet birth.
Though astronomers have cataloged thousands 

of planets orbiting other stars, the very earliest 


stages of planet formation are elusive because 


nascent planets are born and embedded inside vast, 


pancake-shaped disks of dust and gas encircling 


newborn stars, known as circumstellar disks.
The conclusion that planets may betray their 

presence by modifying circumstellar disks on 


large scales is based on detailed computer 

modeling of how gas-and-dust disks evolve 

around newborn stars, which was conducted 

by two NASA Hubble Fellows, Ruobing Dong of 


Lawrence Berkeley National Laboratory, and 


Zhaohuan Zhu of Princeton University. 


Their research was published in the Aug. 


5 edition of 

The Astrophysical Journal Letters.
“It’s difficult to see suspected planets inside 

a bright disk surrounding a young star. Based on 


this study, we are convinced that planets can 


gravitationally excite structures in the disk. 


So if you can identify features in a disk and 

convince yourself those features ar

an underlying planet that you cannot see, 

this would be a smoking gun of forming planets,” Dong said.
Identifying large-scale features produced by planets 

offers another method of planet detection that is 


quite different from all other techniques presently 


used. This approach can help astronomers find 


currently-forming planets, and address when, how, 


and where planets form.
Gaps and rings seen in other circumstellar disks 

suggest invisible planets embedded in the disk. 


However gaps, presumably swept clean by a planet’s 


gravity, often do not help show location of the planet.


Also, because multiple planets together may open 


a single common gap, it's very challenging to estimate 


their number and masses.
Ground-based telescopes have photographed two 

large-scale spiral arms around two young stars, 


SAO 206462 and MWC 758. A few other nearby stars 


also show smaller spiral-like features. “How they 


are created has been a big mystery until now.  


Scientists had a hard time explaining these features,


” Dong said. If the disks were very massive, they would 


have enough self-gravity to become unstable and set up 


wave-like patterns. But the disks around SAO 206462 


and MWC 758 are probably just a few percent of 


the central star’s mass and therefore are not 


gravitationally unstable.
The team generated computer simulations of the 

dynamics of a disk and how the star’s radiation 


propagates through a disk with embedded planets. 


This modeling created spiral structures that very 


closely resemble observations. The mutual gravitational 


interaction between the disk and the planet creates 


regions where the density of gas and dust increases, 


like traffic backing up on a crowded expressway. 


The differential rotation of the disk around the star 


smears these over-dense regions into spiral waves. 


Although it had been speculated that planets can 


produce spiral arms, we now think we know how.

A computer model reproduces the two-spiral-arm structure; the "x" is the Location 
of a putative planet. The planet, which cannot be seen directly, 
probably excites the two spiral arms.
Credits: NASA/ESA/ESO/M. Benisty et al. Univ. of Grenoble/R. Dong, 
Lawrence Berkeley National Lab/Z. Zhu, Princeton Univ.


“Simulations also suggest that these spiral arms have 

rich information about the unseen planet, revealing 

not only its position but also its mass,” Zhu said. 

The simulations shows, the unseen planet would have 

to be bulky, at least 10 times the mass of Jupiter, 

the largest planet in our solar system. that if there 

were no planet present, the disk would look smooth. 

To make the grand-scale spiral arms seen in 

the SAO 206462 and MWC 758 system

the unseen planet would have to be bulky, 

at least 10 times the mass of Jupiter, 

the largest planet in our solar system.



Observations taken by the European Southern Observatory's Very Large Telescope show 
a protoplanetary disk around the young star MWC 758. The disk has two spiral arms 
that extend over 10 billion miles from the star.
Credits: NASA/ESA/ESO/M. Benisty et al. Univ. of Grenoble/R. Dong, 
Lawrence Berkeley National Lab/Z. Zhu, Princeton Univ.


The first planet orbiting a normal star was identified 

in 1995. Thanks to ground-based telescopes and 

NASA’s Kepler mission, a few thousand exoplanets 

have been cataloged to date. But because the planets 

are in mature systems, many millions or a few billion 

years old, they offer little direct clues 

as to how they formed.
“There are many theories about how planets form 

but very little work based on direct observational 

evidence confirming these theories,” Dong said. 

“If you see signs of a planet in a disk right now, 

it tells you when, where, and how planets form.”
Astronomers will use the upcoming NASA James Webb 

Space Telescope to probe circumstellar disks and look 

for features, as simulated by the modeling, and will 

then try to directly observe the predicted planet 

causing the density waves.


For more information, visit:

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4488 / 410-338-4514
villard@stsci.edu


Last Updated: Oct. 29, 2015
Editor: Ashley Morrow

Tags:  Distant Planets, Goddard Space Flight Center, 
Hubble Space Telescope, Stars, Universe